I would personally stay away from DDR.. for the first round of chipsets anyway...
Don't go ALL scsi.. scsi HD's are wayyy to expensive... but everything else scsi is a nice way to go.. if you plan on having lotsa extra stuff like zip, scanner, dvd/cd, etc... if not, don't bother. I had an old HP scanner, zip, cd, dvd, cdr, backup HD at one time (since then dropped to cdr/dvd). its nice to not have everything on the ide chain.. not too mention i had two HD's in there. just my 2 cents.
Dunno about the santaCruz... drivers just don't seem to be there... just go for an older Live/Value.
Go tbird 1.1.. $240!!!!!
IBM HD's
Plextor CDRW
AND DON'T SKIMP ON YOUR CASE. A cheap case in the end will cause mucho trouble... well, it has for me anyway. Another vote for seph's choice PS.. as i have the same one.. very nice.
Enjoy building... the other idea is of course to buy an emachine and give me the leftover dough 🙂